PHYSICAL SCIENCES (CHEMISTRY)
PAPER TWO (P2) 
GRADE 12
NSC EXAM PAPERS AND MEMOS
NOVEMBER 2016

INSTRUCTIONS AND INFORMATION 

1. Write your centre number and examination number in the appropriate spaces  on the ANSWER BOOK.
2. This question paper consists of TEN questions. Answer ALL the questions in  the ANSWER BOOK.
3. Start EACH question on a NEW page in the ANSWER BOOK.
4. Number the answers correctly according to the numbering system used in this  question paper.
5. Leave ONE line between two subquestions, for example between  QUESTION 2.1 and QUESTION 2.2.
6. You may use a non-programmable calculator.
7. You may use appropriate mathematical instruments.
8. You are advised to use the attached DATA SHEETS.
9. Show ALL formulae and substitutions in ALL calculations.
10. Round off your final numerical answers to a minimum of TWO decimal places.
11. Give brief motivations, discussions et cetera where required.
12. Write neatly and legibly.

QUESTIONS

QUESTION 1: MULTIPLE-CHOICE QUESTIONS 
Various options are provided as possible answers to the following questions. Write  down the question number (1.1–1.10), choose the answer and make a cross (X) over  the letter (A–D) of your choice in the ANSWER BOOK. 
EXAMPLE: 
1.11     
1.1 In a chemical reaction an oxidising agent will … 

1. lose protons.
2. gain protons.
3. lose electrons.
4. gain electrons. (2) 

1.2 A catalyst is added to a reaction mixture at equilibrium. 
Which ONE of the following statements about the effect of the catalyst is  FALSE? 

1. The rate of the forward reaction increases.
2. The rate of the reverse reaction increases. 
3. The equilibrium position shifts to the right.   
4. The equilibrium position remains unchanged. (2) 

1.3 What product will be formed when an alkene reacts with water vapour (H2O)  in the presence of an acid catalyst? 

1. Ester
2. Alkane 
3. Alcohol 
4. Aldehyde (2) 

1.4 Which ONE of the following represents a SUBSTITUTION REACTION? 

1. CH₂ = CH₂ + HBr → CH₃CH₂Br
2. CH₂ = CH₂ + H₂O → CH₃CH₂OH 
3. CH₃CH₂OH → CH₂ = CH₂ + H₂O  
4. CH₃CH₂OH + HBr → CH₃CH₂Br + H₂O (2) 

1.5 Consider the two organic molecules I and II below. 

Which ONE of the following represents the homologous series to which  compound I and compound II belong?  (2) 

1.6 Consider the balanced equations for three reactions represented below: 

1. N₂(g) + 3H₂(g) ⇌ 2NH₃(g) 
2. 4NH₃(g) + 5O₂(g) ⇌ 4NO(g) + 6H₂O(g)
3. 2NO(g) + O₂(g) ⇌ 2NO₂(g) 

Which of the above reactions form(s) part of the Ostwald process? 

1. I only
2. II only
3. III only
4. II and III only (2) 

1.7 Which ONE of the following pairs is NOT a conjugate acid-base pair? 

1.  H₃O⁺ and OH⁻
2.  NH₄⁺ and NH₃ 
3. H₂PO₄^- and HPO₄^2-
4. H₂CO₃ and HCO₃^- (2)

1.8 The reaction between hydrogen gas and iodine gas reaches equilibrium in a  closed container according to the following balanced equation: 
H₂(g) + I₂(g) ⇌ 2HI(g) 
Which ONE of the graphs below shows the relationship between the amount  of HI(g) at equilibrium and the pressure in the container at constant  temperature? (2) 

1.9 Which ONE of the equations below represents the half-reaction occurring at  the CATHODE of an electrochemical cell that is used to electroplate an  object? 

1. Ag → Ag⁺ + e^- 
2. Cr³⁺ + 3e^- → Cr
3. Cr³⁺ + e^- → Cr²⁺ 
4. Cu²⁺ + e^- → Cu⁺ (2)   

1.10 Equal amounts of magnesium (Mg) powder react respectively with equal  volumes and equal concentrations of HCℓ(aq) and H₂SO₄(aq), as shown below. 

The magnesium is in EXCESS. 
Consider the following statements regarding these two reactions: 

1. The initial rate of the reaction in test tube X equals the initial rate of the  reaction in test tube Y. 
2. After completion of the reactions, the mass of magnesium that remains  in test tube X will be greater than that in test tube Y. 
3. The amount of hydrogen gas formed in X is equal to the amount of  hydrogen gas formed in Y. 

Which of the above statements is/are TRUE? 

1. I only
2. II only
3. III only 
4. I and III only (2)

[20] 

QUESTION 2 (Start on a new page.) 
The letters A to F in the table below represent six organic compounds. 

2.1 Write down the LETTER that represents the following: 

2.1.1 A hydrocarbon (1)
2.1.2 A functional isomer of compound F (1) 
2.1.3 A compound which belongs to the same homologous series as  compound B (1) 
2.1.4 A plastic (1)

2.2 Write down the STRUCTURAL FORMULA of EACH of the following:

2.2.1 Compound C (3)
2.2.2 The acid used to prepare compound B (2)
2.2.3 The monomer used to make compound D (2)

2.3 Compound A reacts with an unknown reactant, X, to form 2-methylpropane. Write down the: 

2.3.1 NAME of reactant X (1) 
2.3.2 Type of reaction that takes place (1)

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QUESTION 3 (Start on a new page.) 
The boiling points of three isomers are given in the table below. 

3.1 Define the term structural isomer. (2) 
3.2 What type of isomers (POSITIONAL, CHAIN or FUNCTIONAL) are these  three compounds? (1) 
3.3 Explain the trend in the boiling points from compound A to compound C. (3) 
3.4 Which ONE of the three compounds (A, B or C) has the highest vapour  pressure? Refer to the data in the table to give a reason for the answer. (2) 
3.5 Use MOLECULAR FORMULAE and write down a balanced equation for the  complete combustion of compound B. (3)

[11]

QUESTION 4 (Start on a new page.) 
Butane (C₄H₁₀) is produced in industry by the THERMAL cracking of long-chain  hydrocarbon molecules, as shown in the equation below. X represents an organic  compound that is produced. 
C₁₀H₂₂ → X + C₄H₁₀ 
4.1 Write down: 

4.1.1 ONE condition required for THERMAL cracking to take place (1)
4.1.2 The molecular formula of compound X (1)
4.1.3 The homologous series to which compound X belongs (1) 

4.2 A mixture of the two gases, compound X and butane, is bubbled through bromine water, Br₂(aq), in a conical flask, as illustrated below. THE  REACTION IS CARRIED OUT IN A DARKENED ROOM.  

The colour of the bromine water changes from reddish brown to colourless when the mixture of the two gases is bubbled through it. 
Which ONE of the gases (X or BUTANE) decolorises the bromine water?  Explain the answer. (4) 
4.3 Study the flow diagram below, which represents various organic reactions,  and answer the questions that follow. 

Write down the: 

4.3.1 IUPAC name of compound P (2)
4.3.2 Type of reaction labelled I (1)
4.3.3 Structural formula of compound Q (2) 
4.3.4 The type of addition reaction represented by reaction III (1)

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QUESTION 5 (Start on a new page.) 
Hydrogen peroxide, H₂O₂, decomposes to produce water and oxygen according to the  following balanced equation: 
2H₂O₂(ℓ) → 2H₂O(ℓ) + O₂(g) 
5.1 The activation energy (EA) for this reaction is 75 kJ and the heat of reaction  (ΔH) is –196 kJ. 

5.1.1 Define the term activation energy. (2) 
5.1.2 Redraw the set of axes below in your ANSWER BOOK and then  complete the potential energy diagram for this reaction.  
Indicate the value of the potential energy of the following on the y-axis: 

Related Items

• • Activated complex
  • Products                                (3) 
    (The graph does NOT have to be drawn to scale.) 
    

When powdered manganese dioxide is added to the reaction mixture, the rate  of the reaction increases.  

5.1.3 On the graph drawn for QUESTION 5.1.2, use broken lines to  show the path of the reaction when the manganese dioxide is  added. (2) 
5.1.4 Use the collision theory to explain how manganese dioxide  influences the rate of decomposition of hydrogen peroxide. (3) 

5.2 Graphs A and B below were obtained for the volume of oxygen produced over time under different conditions.

5.2.1 Calculate the average rate of the reaction (in dm³∙s^-1) between  t = 10 s and t = 40 s for graph A. (3) 
5.2.2 Use the information in graph A to calculate the mass of hydrogen  peroxide used in the reaction. Assume that all the hydrogen  peroxide decomposed. Use 24 dm³·mol^-1 as the molar volume of  oxygen. (4) 
5.2.3 How does the mass of hydrogen peroxide used to obtain graph B compare to that used to obtain graph A? Choose from GREATER  THAN, SMALLER THAN or EQUAL TO. (1) 

5.3 Three energy distribution curves for the oxygen gas produced under different  conditions are shown in the graph below.  
The curve with the solid line represents 1 mol of oxygen gas at 90 °C. 

Choose the curve (P or Q) that best represents EACH of the following situations: 

5.3.1 1 mol of oxygen gas produced at 120 °C (1) 
5.3.2 2 moles of oxygen gas produced at 90 °C (1)

[20] 

QUESTION 6 (Start on a new page.) 
Hydrogen gas, H₂(g), reacts with sulphur powder, S(s), according to the following  balanced equation: 
H₂(g) + S(s) ⇌ H₂S(g) ∆H < 0 
The system reaches equilibrium at 90 °C. 
6.1 Define the term chemical equilibrium. (2) 
6.2 How will EACH of the following changes affect the number of moles of H₂S(g)  at equilibrium?  
Choose from INCREASES, DECREASES or REMAINS THE SAME. 

6.2.1 The addition of more sulphur (1) 
6.2.2 An increase in temperature 
Use Le Chatelier's principle to explain the answer. (4) 

6.3 The sketch graph below was obtained for the equilibrium mixture. 

A catalyst is added to the equilibrium mixture at time t₁.  
Redraw the graph above in your ANSWER BOOK. On the same set of axes,  complete the graph showing the effect of the catalyst on the reaction rates. (2) 
Initially 0,16 mol H₂(g) and excess S(s) are sealed in a 2 dm3 container and the system is allowed to reach equilibrium at 90 °C.  
An exact amount of Pb(NO₃)2 solution is now added to the container so that ALL the  H₂S(g) present in the container at EQUILIBRIUM is converted to PbS(s) according to  the following balanced equation:  
Pb(NO₃)₂(aq) + H₂S(g) → PbS(s) + 2HNO₃(aq) 
The mass of the PbS precipitate is 2,39 g.  

6.4 Calculate the equilibrium constant Kc for the reaction H₂(g) + S(s) ⇌ H₂S(g)  at 90 °C. (9)

[18] 

QUESTION 7 (Start on a new page.) 
7.1 A learner dissolves ammonium chloride (NH₄Cℓ) crystals in water and  measures the pH of the solution. 

7.1.1 Define the term hydrolysis of a salt. (2) 
7.1.2 Will the pH of the solution be GREATER THAN, SMALLER THAN or EQUAL TO 7? Write a relevant equation to support your answer. (3) 

7.2 A sulphuric acid solution is prepared by dissolving 7,35 g of H₂SO₄(ℓ) in  500 cm³ of water.  

7.2.1 Calculate the number of moles of H₂SO₄ present in this solution. (2) Sodium hydroxide (NaOH) pellets are added to the 500 cm³ H₂SO₄ solution. The balanced equation for the reaction is: 
H₂SO₄(aq) + 2NaOH(s) → Na₂SO₄(aq) + 2H₂O(ℓ) 
After completion of the reaction, the pH of the solution was found to be 1,3. Assume complete ionisation of H₂SO₄. 
7.2.2 Calculate the mass of NaOH added to the H₂SO₄ solution. Assume  that the volume of the solution does not change. (9)

[16]

QUESTION 8 (Start on a new page.) 

8.1 A nickel (Ni) rod is placed in a beaker containing a silver nitrate solution,  AgNO₃(aq) and a reaction takes place. 

Write down the: 

8.1.1 NAME or FORMULA of the electrolyte (1)
8.1.2 Oxidation half-reaction that takes place (2) 
8.1.3 Balanced equation for the net (overall) redox reaction that takes  place (3) 

8.2 A galvanic cell is now set up using a nickel half-cell and a silver half-cell. 

8.2.1 Which electrode (Ni or Ag) must be connected to the negative  terminal of the voltmeter? Give a reason for the answer. (2) 
8.2.2 Write down the cell notation for the galvanic cell above. (3) 
8.2.3 Calculate the initial reading on the voltmeter if the cell functions under standard conditions. (4) 
8.2.4 How will the voltmeter reading in QUESTION 8.2.3 be affected if  the concentration of the silver ions is increased? Choose from INCREASES, DECREASES or REMAINS THE SAME. (1)

[16] 

QUESTION 9 (Start on a new page.) 
In the electrochemical cell below, carbon electrodes are used during the electrolysis of  a concentrated sodium chloride solution. 

The balanced equation for the net (overall) cell reaction is: 
2H₂O(ℓ) + 2Cℓ^─(aq) → Cℓ₂(g) + H₂(g) + 2OH^─(aq) 

9.1 Is the reaction EXOTHERMIC or ENDOTHERMIC? (1)
9.2 Is electrode P the ANODE or the CATHODE? Give a reason for the answer. (2)

9.3 Write down the: 

9.3.1 NAME or FORMULA of gas X (1)
9.3.2 NAME or FORMULA of gas Y (1)
9.3.3 Reduction half-reaction (2) 

9.4 Is the solution in the cell ACIDIC or ALKALINE (BASIC) after completion of  the reaction? Give a reason for the answer. (2)

[9] 

QUESTION 10 (Start on a new page.) 
10.1 The flow diagram below shows the processes involved in the industrial  preparation of fertiliser Q.  

Write down the: 

10.1.1 Name of process X (1)
10.1.2 Name of process Y (1)
10.1.3 NAME or FORMULA of gas P (1)
10.1.4 Balanced equation for the formation of compound B (3)
10.1.5 Balanced equation for the formation of fertiliser Q (4) 

10.2 The diagram below shows a bag of NPK fertiliser of which the NPK ratio is  unknown. It is found that the mass of nitrogen in the bag is 4,11 kg and the  mass of phosphorus is 0,51 kg. 

Calculate the NPK ratio of the fertiliser. (4)

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TOTAL: 150 

DATA FOR PHYSICAL SCIENCES GRADE 12 
PAPER 2 (CHEMISTRY) 
TABLE 1: PHYSICAL CONSTANTS

TABLE 2: FORMULAE

TABLE 3: THE PERIODIC TABLE OF ELEMENTS 

TABLE 4A: STANDARD REDUCTION POTENTIALS

TABLE 4B: STANDARD REDUCTION POTENTIALS